I got bored and figured I would do this also. Here is a shorter version of your script

on *:text:.*:#:{
  if ($1 == .sart) {
    play stop
    return
  }
  if ($1 == .rart) {
    play $chan $+(",$findfile(mircart, *.txt, $rand(1, $findfile(mircart, *.txt, 0))),") 500
    return
  }
  else { 
    play $chan mircart/ $+ $deltok( $+ $1 $+ ,0,46) $+ .txt 500
  }
}